void main(List<String> args) {
  Person p1 = Person('kate',45);
  p1.say();
}
class Person{
  
  String name = '1';
  int age = 18;
  /*
  Person (String n, int a){
    name = n;
    age = a;
  }*/
  //支持语法糖
  Person(this.name,this.age);
  Person.create(String n, int a){
    name = n;
    age = a;
  }
  void say(){
    print('say$name:$age');
  }
}